A display device is an apparatus which visually displays information such as text, images or color. Flat display devices that have little limitation on installation space because they reduce high weight and volume which are disadvantages of cathode ray tubes, are easy to display large screen images and to provide flatness and exhibit superior functions such as high image quality are developed, which enable miniaturization and portability of display devices and combination of the display devices with other devices.
Most of flat display devices implement color by filling a material, properties of which change upon application of an electric field between an upper electrode and a lower electrode and applying a voltage to the upper electrode and the lower electrode.